It is desired to acquire a high degree of capacity in wireless communication networks. One technique to increase capacity in a wireless communication network is to deploy low power pico radio base stations within macro cell coverage areas forming a heterogeneous network. Pico base stations are smaller than regular macro base stations, and cover smaller areas, and are in many cases placed close to street level and a backhaul aggregation point is usually placed at macro base stations above rooftop level.
Traditional backhaul technologies for establishing a connection between pico base stations and a backhaul aggregation point are line-of-sight radio links. However, when the backhaul aggregation points are placed above rooftop level while the pico base stations are below the roof, closer to the street level, line-of-sight (LOS) may be prevented such that a none line-of-sight (NLOS) scenario exists. Then, one cannot align the radio link backhaul antenna beams at the macro base station and the radio link backhaul antenna beam at the pico base station towards each other by means of visual inspection and manual adjustment. Traditionally, backhaul connection has then been solved by using for example copper wires or optical fiber wires.
However, the traditional backhaul technologies discussed above do not always fit a heterogeneous backhaul scenario. High gain, narrow beam antennas are desired in wireless backhaul applications to connect for example a fixed backhaul aggregation point at a macro base station with a fixed pico base station in a heterogeneous network scenario. In order to cover a number of pico base stations, the macro sites need to be equipped with one antenna for each pico base station to connect. This is undesirable due to visual impact as well as economical reasons. Wireless NLOS backhaul radio links equipped with multi-beam antennas have then been proposed as an alternative.
Aligning sensor antennas, using a multi-beam antenna in free space, is for example described in US 2004/0066325 where a wide beam antenna at a central node is used to cover a broad sector containing a number of remote nodes. The antenna alignment is relatively easy to perform since there is a visual connection between the nodes.
However, how to simultaneously align multi-beam and narrow beam radio link antennas is not taught, and there is thus a need for such a method.